Circuit breaker having improved trip unit



June 28, 1966 A. E. MAIER CIRCUIT BREAKER HAVING IMPROVED TRIP UNIT Filed Sept. 28, 1964 5 Sheets-Sheet l 0 M a. WP 1.1 r, M I m (I! I I fig C f 3 r Md v V M .m w I B I H e @1 M w m 1 H W,

June 28, 1966 A. E. MAIER cIRcUIT BREAKER HAVING IMPROVED TRIP UNIT Filed Sept. 28, 1964 5 Sheets-Sheet 2 June 28, 1966 A. E. MAIER CIRCUIT BREAKER HAVING IMPROVED TRIP UNIT 5 Sheets-Sheet 3 Filed Sept. 28, 1964 June 28, 1966 A. E. MAIER 3,258,561

CIRCUIT BREAKER HAVING IMPROVED TRIP UNIT Filed Sept. 28, 1964 5 Sheets-Sheet 4 Q 221 @**192 I. V

United States Patent 3,258,561 CIRCUIT BREAKER HAVING IMPROVED TRIP UNIT Alfred E. Maier, Colonia, N.J., assignor to Federal Pacific Electric Company, a corporation of Delaware Filed Sept. 28, 1964, Ser. No. 399,767 16 Claims. (Cl. 200- 83) This invention relates to circuit breakers, and more particularly, to molded-case multi-pole circuit breakers with self-contained overcurrent release means.

Heretofore, circuit breakers of the class described have utilized magnetically operated trips for instantaneous operation on the occurrence of severe short circuit and thermally operated trips for longer time delays at lower overloads. This arrangement, while satisfactory for severe overloads and low overloads, is less than satisfactory for intermediate overloads. It is an object of this invention to provide a molded case circuit breaker responsive to low, intermediate and severe overloads. Further, thermally operated trips are inherently temperature responsive and are sensitive to the circuit breaker ambient as well as to the temperature of the portion of the current path through the circuit breaker that they are designed to monitor. In order to eliminate ambient sensitivity the use of extremely complex compensating structures has been proposed. These have been found to be of doubtful eflicacy. It is an object of this invention to improve the stability of the tripping characteristic of the circuit breakers by eliminating the source of ambient temperature sensitivity. A feature of this invention is the provision of a circuit breaker incorporating overcurrent responsive means which is nonresponsive to ambient temperature variations over a wide range. It is a further object of this invention to provide a circuit breaker having interchangeable trip means whose tripping characteristic remains virtually without change when the trip means is exposed to wide variation in temperature at its installed position.

Heretofore widely used molded case circuit breakers have been provided with instantaneous and long time delay trips, as defined in the art, with no definite provision for shorter time delays as would be needed at overloads intermediate those effecting long time delays and instantaneous responses. Where the short time delay was not provided, the electrical apparatus protected by the molded case circuit breaker was subjected to the intermediate overloads for a longer time than desirable. It is therefore a further object of this invention to improve the trip characteristics of molded case circuit breakers by providing for time delays intermediate those classified as long and instantaneous. It is yet another object of this invention to provide a trip unit for molded case circuit breakers which trip unit has a combined tripping characteristic providing short time delay, long time delay and instantaneous trip characteristics.

Circuit breakers having more than one pole have required individual calibration of the overcurrent responsive means associated with each pole in order to insure similar response in each pole. This adjustment had been particularly difficult and burdensome in the class of circuit breakers utilizing thermally operated trips. ject of this invention is to provide a multi-pole circuit breaker utilizing overcurrent response means having a common, single, calibration point for each of the various time delays and instantaneous function of each of the poles.

A further :object of the invention is the provision of a trip unit having parallel operating means wherein, in the event of failure of one of the operating means for releasing the circuit breaker latch means, the other will An obice be effective to produce the desired release of the circuit breaker latch means to open the breaker.

A further object of the invention is the provision of a multi-pole circuit breaker having the same tripping sensitivity on sigle pole and multi-pole overloads.

Pursuant to the objects of the invention, the illustrative embodiment described in detail below utilizes a hydraulic system that is not ambient responsive to interconnect overcurrent sensing elements at each of the poles of the circuit breaker with a single output element. The output element is operatively connected to the releasable means used for separating the pairs of contacts of the circuit breaker.

The above and other objects, features and advantages of the invention will be more fully understood from the following description taken in conjunction with the accompanying drawings in which:

FIG. I is a top plan view of a multi-pole circuit breaker according to the present invention, with the cover shown removed;

FIG. II is a sectional view taken on the line IIII of FIG. I;

FIG. III is a sectional view taken along the line III-III of FIG. I;

FIG. IV is a sectional view taken along the line IVIV of FIG. 1;

FIG. V is a sectional view taken along the line V-V of FIG. I;

FIG. VI is a sectional view taken along the line VI-VI of FIG. I;

FIG. VII is a sectional view taken along the line VII VII of FIG. I;

FIG. VIII is a vertical sectional view taken along the line VIIIVIII of FIG. I;

FIG. IX is an enlarged vertical sectional view showing a portion of the tripping mechanism, said view being taken along the line IX-IX of FIG. 1;

FIG. X is an enlarged elevation of the tripping mechanism shown in FIG. IX viewed from the left side thereof;

FIG. XI is a top plan view of another embodiment of the overcurrent trip;

FIG. XII is a vertical section view taken on the line XII-XII of FIG. XI with some parts in section and with other parts broken away; and

FIG. XIII is a vertical sectional view, similar to FIG. XII, of yet another embodiment of the overcurrent trip.

Referring to the drawings and more particularly to FIGS. I and II thereof, there is shown a three-pole circuit breaker It), each pole A, B and C comprising a pair of terminals 12 and 14 disposed at opposite ends of the breaker. The circuit breaker includes a base 16 of molded insulating material on which the components of the breaker mechanism are mounted. A cover 18 of molded insulating material is removably secured to the base 16 and cooperates therewith to form an enclosing housing for the breaker mechanism. The circuit breaker is provided at each pole with two associated pairs of stationary and movable main contacts 20 and 22, respectively, an associated pair of stationary and movable arcing contacts 24 and 26, respectively, and an arc chute 27 having a number of arc splitter plates '28. Each of the movable main contacts 22 is mounted on a contact block 30 and the movable arcing contact 26 is mounted on an arcing contact block 32 having an arcing tip 34 extending into arc chute 27. Thus, each pole is provided with a pair oTblocks 30 and a block 32 disposed in side-by-side relation with the latter block disposed between the former blocks. The blocks 30 and 32 of each pole are pivotally mounted on a carrier 36 for the movable contacts by pivot pin 38, the latter extending through the spaced legs 40 of said contact carrier 36 and said blocks. The arc-ingcontact block 32 is biased downwardly to bias contact 26 into pressure engagement with companion arcing contact 24 by compression spring 42 seated in fitting and secured to the base plate 46 of the contact carrier 36. A threaded shaft 48 extends upwardly of the arcing block through a suitable aperture provided therefor in plate 46 and receives a nut 50 which coacts with said plate to form a stop limiting pivotal movement of the arcing block on contact opening. Contact pressure for each of the contact blocks 30 is developed by compression spring 52 seated at one end of fitting 54 secured to plate 46. The opposite end of spring 52 is seated in a recess 56 of the contact block, the latter having a threaded shaft 58 extending upwardly therefrom through the spring. A nut 60 and shaft 58 form a stop for limiting pivotal movement of the block 30 on contact opening.

The movable contact carrier 36 is pivotally mounted in a companion frame 62 by pivot pin 64 for movement between circuit open and closed positions. The three contact carriers 36 are operated by two actuating mechanisms indicated generally at 66 to be described in detail hereinafter. Each of the poles of the breaker is contained in a separate compartment formed by interphase barriers 68 and 69 in the base and cover which extend longitudinally of the breaker. The movable contact carriers 36 are rigidly interconected for conjoint movement by the main tie or torque bar 70 and supplementary tie or torque bar 72, the bars being insulation covered and extending across all the poles of the breaker through the barriers 68, 69. The tie bars are suitably secured to the plates 46 of contact carriers 36 by brackets 74, 75. The tie bar 72 is secured to the contact carriers 36 remote from the pivotal mounting thereof to make the contact carrier assembly a more nearly rigid unit to obtain the desired equal distribution of the operating torque among the contact carriers 36.

The pair of actuating mechanisms 66 provide the operating drive for the three contact carriers 36. The actuating mechanisms 66 are alike, each being of the overcenter spring quick-make and quick-break type. Each mechanism 66 comprises a frame 76 suitably secured in the base 16, the frame having in-turned flanges 78 which define stops for the actuating member 80 of inverted U-shape which is pivoted to the frame by pivot pins 82. The knee pin 84 interconnects the pair of upper links 86 and the lower member 88 which extends through an opening provided in the contact carrier 36, the member 88 being secured to the contact carrier by pivot pin 92. The links 86 at their opposite ends are pivotally connected to releasable cradle 94 by pivot pin 96, the cradle being mounted on a shaft 98 that pivots in frame 76. A pair of tension springs 100 (only one shown) extend between knee pin 84 and the actuating member 80. The cradle 94 is provided with a latch part 102 having an inclined face, which is latched by the trip mechanism to be described, when the circuit breaker is closed. During both the manual opening and closing operations of the circuit breaker, the cradle remains latched. On circuit closing movement of the actutaing member 80, the lattertension springs 100 of the toggle and on overcentering of the springs the contact carriers 36 are actuated to closed position. On circuit opening movement of the actuating member 80 the toggle collapses at the knee 84 to move the contact carriers 36 to circuit open position. In a closed circuit condition, the release of the cradle by the tripping mechanism results in the rotation of the cradle about its pivot and overcentering of the springs to break the toggle and open the circuit breaker.

The actuating members 80 of mechanism 66 are coupled for simultaneous actuation by the operating handle 104 which extends through an opening 106 provided therefor at the center pole in the cover 18. The hand-le 104 has a bridging part 107 provided with slots for the reception of the coupling plates 1 10, the latter being secured to the bridging part by screws 112. The

two plates 1.10 at each end of the bridging part grip a leg 114 of respective actuating member so that operation of the handle 104 will directly drive actuating members 80 in unison to actuate the coupled contact carriers 36 of each of the poles. If either mechanism 66 should start to over-center infinitesimally earlier than the other during deliberately gradual operation, the tie bars nevertheless retard the opening operation of the first mechanism and expedite opening operation of the second as soon as dead center is passed.

The contacts 20 and 24 are in circuit with terminal 12 through the contact plate 116 and the contact blocks 30 and 32 are electrically connected to the conductor 118 by conductors 120. The conductor 118 is in circuit with terminal 14. It will be noted that the tie bar 72 carries interphase barrier elements 122 at the barriers 68, 69, so that bar 72 can move freely in slots 123 in these barriers while blocking the slots. Tie bar 72 is united to the contact carriers 36 of the outer poles by bracket 75 and to carrier 36 of the center pole by an inverted U member 124 that is staked to its carrier 36.

The trip device or mechanism 126 normally serves to restrain the actuating mechanisms 66 in the latched condition. It is operable in response to an overload in the circuit controlled by the breaker to elfect release of both actuating mechanisms and thus automatically open all of the movable contacts of the breaker. The trip mechanism 126 is a unitary structure being removably secured in the breaker casing as by screws 130. Referring to FIGS. I, II and III, at each pole of the breaker there is provided a magnetically responsive overcurrent sensing means 132. The magnetically responsive means 132 at each pole comprises a U-shaped core of magnetic material and a companion movable armature 142. Armature 142 is mounted for movement with respect to the core by means of its pivoted engagement, at shoulder 143, with a guide plate 144 that is mounted on the trip mechanism. The armature is biased away from the core, against adjustment screw 145, by means of spring 146 interposed between the armature extension 148 and the guide plate 144. Adjustment screw sets the initial air gap between the armature 142 and core 140 and thereby adjusts the initial pick-up point of the armature. A bolt 134 connects each conductor 1 18 to a companion terminal 14. A portion .150 of the conductor 118 passes through the core 140 and forms an energizing vwinding for the electromagnetic trip means. A layer of insulation 152 is interposed between the core and strip portion 150.

The trip mechanism 126 further includes an input element 154 for each of the poles and a single output element 156. Output element 156 engages a portion of latch 158, to be described in detail below, and operates the latch upon the occurrence of predetermined overload condition. The body of the trip mechanism comprises two blocks 160, 162 of insulating material which are complementary in configuration. A formed flexible diaphragm 164 as of rubber is interposed between the blocks and is retained therebetween by screws 166 that serve to secure the blocks together thus forming a sealed hydraulic unit as will be explained below.

In a three pole circuit breaker, three input elements 154 are used. Since the three input elements 154 are identical only one will be described in detail. Input element 154 (FIG. III) includes a piston 168 and piston rod 170 adapted to engage the armature extension 148 of its respective pole. The end of the extension 148 is notched at 171 and a reduced diameter portion of the rod 170 having a shoulder 172 is received therein. Pivotal movement of the armature, when attracted by the core, is translated into reciprocating movement of the piston rod and piston. Piston 16-8 is movable in a chamher 174 formed of bore 176 in the block 160 and of bore 178 in block 16 2 (FIG. VIII). vPiston 168 engages a dome-shaped portion 180 of the formed diaphragm 164.

In the illustrative embodiment, diaphragm 164 extends across the entire interface between the blocks 160, 162 of the input element positions and, similarly, at the output element position. The dome-shaped portions may be characterized as active portions of the diaphragm as compared to the passive portions of the diaphragm constrained between the opposed surfaces of the blocks 160, 162. In each case, the active diaphragm portion 180 separates the respective bores 176, 178 and serves to isolate them from one another. A fluid-tight chamber 179 is formed by the diaphragm and bore 178 in block 162. The maximum extension of piston rod 170 under the bias of the fluid pressure within the chamber is limited by engagement of shoulder 172 with the armature portion 148, the movement of the armature being stopped by engagement with screw 145.

Output element 156 (FIG. V) includes a piston 182 and piston rod 184. The output piston 182 engages an active portion 186 of the diaphragm 164 in a chamber 188 formed of bores '190, 192 in blocks 160, 162, respectively. A fluid-tight chamber 193 is formed by the diaphragm 164 and bore 192 in block 162. The piston is normally biased by spring 194 to cause the diaphragm 1 86 to closely approach or rest against the bottom wall 192a of the bore 192 and produces the initial pressurization of the fluid system to be described below. This spring bias is adjustable as by varying the compression of spring 194 by screwing collar 196 into or out of threaded insert 198 secured in block 160. The free end of the piston rod is bifurcated at 200 and receives a portion of the latch 158.

In order to provide an interconnecting passageway 202 (FIG. VIII) for the fluid system a groove 204 is formed in block 162 which connects the input element bores 17 8 to one another. Diaphragm 164 overlies the groove in the assembled condition of the trip unit and completes the fluid-tight communicating passageway 202.

Referring to FIGS. IV and VIII, there is illustrated means for providing long time delay operation of the output element 156. Passageway 206 formed by a groove 208 in block 162 and diaphragm 164 interconnects the input passageway 202 and the bore 192 of the output element 156. Groove 208 has an intermediate broadened portion 210 that cooperates with a portion 212 of the diaphragm 164 to provide an adjustable fluid-flow restricting constriction or valve 214 in passageway 206. The diaphragm portion 212, which forms one wall of the passageway 204, is movable toward the wall 211 in block 162 by an adjustable member 216 loosely secured to screw 218 that threadedly engages block 160. Member 216 is of such a size and configuration as to be able to close off fluid flow through the passageway when driven against wall 211. Member 216 may be withdrawn into a bore 220 formed in block 160 opposite the widened groove portion 210 to adjust the degree of constriction in passageway 206.

Referring to FIGS. VI and VII, there is illustrated means for providing instantaneous operation of the output element 156. A pair of passageways 220, 221 (FIG. VIII) are formed by grooves 222, 223 in block 162 and diaphragm 164. The passageways 220, 221 serially connect the input passageway 202 and the bore 192 of the output element 156. Grooves 222, 223 are separated by an intermediate transverse wall 224 that extends to the plane of the surface of the block 162. A bore 226, formed in block 160 opposite transverse wall 224, is slightly wider than the transverse wall 224 which is diametrically located with respect to the bore. Diaphragm portion 228 overlies the wall 224 and separates the junction of the grooves 222, 223 from bore 226. Piston 230 is biased by spring 232 against the diaphragm portion 228. The diaphragm closes off the passageways 220, 221 from one another when against the upper surface of the wall 224. When sufiicient fluid pressure is generated within the passageways 202 and 220 by operation of one or more input elements 154, the piston is displaced within the bore 226 against the bias of spring 232 and fluid flow into passageway 221 is possible. The aforedescribed structure forms an adjustable fluidpressure responsive valve 234. The operating or releasing pressure of the valve 234 is determined by the bias of spring 232. This bias is controlled by adjustable means including a screw member 236 that threadedly engages block 160.

Adverting to FIGS. VII and VIII, there is illustrated means for providing short time delay operation of the output element 156. Passageway 237, formed by groove 238 in block 162 and diaphragm 164, interconnects the input passageway 202 and the passageway 221 previously described. Groove 238 has an intermediate broadened portion 239 that cooperates with a segment 240 of the diaphragm 164 to provide an adjustable fluid-flow restricting constriction or valve 241 in passageway 237. The diaphragm portion 240, which forms one wall of the passageway 237, is movable toward the wall 242 in block 162 by an adjustable member 243 loosely secured to screw 244 that threadedly engages block 160. Member 243 is of such a size and configuration as to be able to close off fluid-flow through the passageway when it drives the diaphragm portion 240 against wall 242. Blocking member 243 may be withdrawn into a bore 245 formed in block 160. Direct connection of passageways 237 and 221 is prevented by the interposition of an adjustable fluid pressure responsive valve 246. Valve 246 is similar in construction and mode of operation to the valve 234 previously described and includes diaphragm portion 247 that biased against transverse wall 248 by piston 249. Bias spring 250 reacts between the piston 249 and a screw member 251 threaded into the block 160. The series combination of flow restricting valve 241 and pressure responsive valve 246 provides adjustable short time delay operation of the trip unit as will be explained below in detail.

The passageways and the various bores are filled with a suitable hydraulic fluid such as silicon oil of proper viscosity through ports 252 (FIG. VIII) that are appropriately placed. The silicon oils employed herein are normally insensitive to temperature variation over the range to which circuit breakers are exposed. There is no appreciable change in volume or in viscosity in this range thereby eliminating sensitivity to ambient temperature variations. The contained air in the trip unit is bled from the system during the filling operation. At the time of filling the pistons 168 of the input elements 154 assume their no input position with the piston rod 170 extended and the armatures 142 against the stop 145. The resilience of the formed portion of the diaphragm assists this positioning. The volume of the chamber 179 formed by the diaphragm portion 180 and bore 178 is at its maximum at this time. The piston 182 of the output element 156 is urged to its no output position adjacent the bottom of bore 192 by spring 194 which overcomes the resilience of the diaphragm portion 186. The volume of fluid contained in the chamber 193 formed by the diaphragm 186 and the bore 192 is then at a minimum. The respective volumes of the input element chambers 179 and output element chamber 193 are substantially equal. Ports 252 are closed after filling by suitable means well known in the art.

Referring to FIGS. I, IX and X the latch mechanism 158 includes at the center pole lever member 253 pivotally mounted on pivot pin 254 carried by the bracket 255 fixed to the outside surface of block 160 by screws 256. A toggle indicated at 257 is formed of two links 258, 259 with the knee of the toggle at their junction. Link 258 of the toggle is secured to lever 253 and is also carried by pivot pin 254. Link 259 is U-shaped and engages link 258 and a depending part 260 of part 261. The toggle formed by links 259, 260 serves to prevent the clockwise rotation of part 261 about its pivot pin 262. Collapse of the toggle 257 is prevented by the engagement of a portion of link 259 at the knee of the toggle with lever 253. Part 261 is also restrained against counterclockwise rotation about pin 262 by the links 259, 260. Spring 263 about pivot pin 7 254 reacts against the link 258 and the frame 255 to bias the toggle toward its erected position. Spring 263 lightly biaseslever 253 toward the back of the bracket 255 by virtue of the end of link 259 which is pivoted in link 258.

Pivot pin 262 is carried by the spaced arms 264, 265 of the bracket. Part 261 is biased counterclockwise (FIG. X) about pin 262 by torsion spring 266 about shaft 262. Spring 266 has two groups of convolutions longitudinally spaced on the shaft and a central straight length 268 in engagement with part 261. The bias of spring 266 is in the toggle 257 erecting direction. The part 261 has a pair of laterally spaced arms 260 and 270 about shaft 262 inboard of arms 264 and 265, said part having an angle-shaped part 272 extending between the arms. Upward bias against the depending part 272 derived from the restrained contact actuating mechanisms, tends to bias part 261 clockwise. On trip actuation latch 158 is operated and, by virtue of lever 253 being pivoted about pin 254, collapses the toggle 257 formed by links 259, 260. Part 261 is no longer restrained when the toggle collapses and is free to rotate clockwise about pin 262 thereby releasing the contact actuating mechanisms for opening the circuit breaker as will be described in detail below.

The base 274 of bracket 255 is secured in the casing by screw 130, the conductor strip 118 being secured in position below base 274 by said screw. Similar screws, not utilized for mechanical mounting of the trip unit, are used in joining the respective conductors 118 of the other poles.

Operatively engaged with part 261 is a part 276 having center portion 276' engaged below part 272 and arms 27 8 provided with insulating mounting elements 280 carried by the ends 282 of shaft 262 (see FIG. 1). Parts 261 and 276 are coaxial and operate as a unit, so that they may be of one-piece construction if desired. In the illustrated embodiment the arms 278 are of metallic construction and are united to the elements 280 of insulation. Laterally projecting from each of the elements 280 is a pin 284 which is received in a companion elongated slot 286 provided in the inner leg 28% of a frame 290. Such frame 290 is provided at each of the outer poles for each of the cradles of the actuating mechanisms. Each frame 290 is pivotally mounted on a shaft 222 carried by a respective frame 76. An elongated latch roller 294 is carried by each frame 2% in the elongated slots 286 thereof, said roller being biased toward the left in FIG. 2 by torsion spring 296. Slots 236 allow the rollers 294 to be displaced to clear the cradle 94 on relatching the latter after having been tripped, by reset operation of handle 104. From the above it will be apparent that the parts 261, 276, 296 and 294 transmit the upward biasing force (FIG. I) applied by the cradles 94 to the trip bar toggle 257. On release of the tripping mechanism at the toggle 257, the otherwise independent cradles 94 of the two actuating mechanisms 66 will both be released and will thus open all of the poles of the breaker.

Only a small fraction of the strong upward biasing force of the cradles 94 is imposed on the trip unit. More particularly, the only force imposed by the actuating mechanism 66 on the trip mechanism is a low magnitude torsion force required to operate the trip mechanism and which is easily resisted by the toggle 257. The circuit breaker operating mechanism heretofore described, except for the trip unit 126, is discussed in detail in Patent No. 3,125,683 Multiple Automatic Circuit Breaker which is assigned to the same assignee as the present invention.

For better understanding of the invention the operation of the trip unit 126 shown in FIGS. I through VIII will be described in its various operative modes. The armature 142 is attractable to the core 140 that surrounds the conductor segment 150. The amount of attractive force generated by the core is directly related to the amount of current flowing through the conductor 118 and is therefore related to the circuit condition. Movement of the armature 142 toward the core 146 is resisted by spring 146 and by the hydraulic system contained within the trip unit 126, i.e., as the armature attempts to move toward the core, the armature extension 148 attempts to move the piston rod 176 of the input element 154 toward the right thus driving piston 168 against the diaphragm section 186. The pick-up point i.e., the level of current flow through conductor 15% at which movement of the armature commences is a function of the air gap between the armature and the core. The initial gap between the armature and the core may be adjusted by screw 145. Movement of the diaphragm toward the right (FIG. III) is resisted by the fluid contained between the diaphragm portion 186 and the block 162 in bore 178. Since the entire fluid system is filled with an incompressible fluid, pressure applied at any input element 154 will be transmitted to the output element 156. The movement of piston 168, under impetus of the magnetic forces generated between the armature and the core, displaces some of the fluid from the bore 173 and into the communicating passageway network. The displaced fluid flows through the network of passageways into the bore 192 of the output element between the diaphragm portion 186 and the bottom wall 1152a. The input pistons 168 of the other poles are restrained against movement that would relieve the fluid pressure by virtue of the engagement of their re spective armatures 142 with the stops 145. Fluid movement into the output element bore 193 displaces diaphragm portion 156 and piston 182 against the bias of spring 194. The aforementioned fluid flow takes place through the communicating passageways only when suflicient pressure has been generated to overcome the bias of spring 194.

Three alternative fluid flow paths are provided in the illustrative embodiment. When the overload is moderate, i.e., from to 400% of the nameplate current rating, then a relatively long time delay is desirable before the breaker trips. The desired time delay characteristic before the operating pressure is reached is achieved by restricting the rate of flow of the displaced fluid through the communicating passageways and through the valve 214 while the pressure responsive valves 234, 246 remain closed. The force required to trip the breaker, and therefore the current level required to trip the breaker is determined by the bias of spring 194 in the output element 156. The fluid pressure developed in the input element 154 is directly proportional to the mechanical output of the current sensing element 132. When the overload is greater than a given magnitude then a larger force is available at the input element and, with a given degree of constriction, a greater flow rate to transmit the pressure to the output element can be achieved thus resulting in operation of the output element 156 within a shorter time. The higher the current the higher the fluid pressure and the shorter the flow time. Thus an inverse time delay characteristic is produced for the trip unit. The degree of constriction and therefore the time versus rate of flow setting may be varied by adjusting the position of part 216 relative to the wall 211 of groove 210.

In the event of a short circuit, in the neighborhood of ten times or more rated current, a very great increase in hydraulic pressure is generated by the forceful movement of the armature toward the core which is not quickly relieved by fluid flow past the constricting valves 214, 241. This increase in hydraulic pressure would normally not be efiiective to cause very rapid operation of the output element but for the provision of the pressure relief valve 234. When the pressure in the system exceeds a predetermined level, then the diaphragm portion 228 of valve 234 is lifted away from the transverse wall 224, against the bias of spring 232, and allows the fluid to flow from passage 220 into passage 221 and to the bore 192 of the output element, thus bypassing the constriction formed at the valves 214, 241, driving the output element piston rod 184 against latch 158 and providing extremely fast response or instantaneous tripping. The current level, i.e., fluid pressure, at which the bypass valve 234 operates may be adjusted by changing the compression of spring 232.

The third fluid path provides time delays that are longer than those classified as instantaneous yet shorter than the long delays described above. For purposes of convenience, such a delay is characterized as short. The third fluid flow path includes constriction valve 241 and pressure relief valve 246 in series. The constriction at valve 241 is set so that it is less than that at valve 214 and pressure relief valve 246 is set to release at a lower pressure than valve 234 described above. Upon the occurrence of severe short circuits such as those that would cause operation of valve 234, the constriction valve 241 impedes the flow of fluid through passageway 237 so that the pressure buildup at valve 246 does not reach the operating pressure until the relief valve 234 has already operated. Therefore, relief valve 234 alone controls instantaneous tripping of the breaker. Likewise, when the fluid pressure is low then the pressure at valve 246 does not build up to its operating point and constriction valve 214 alone controls the operation of the breaker providing the long time delay characteristic. When the fluid pressure is higher than the operating point of the relief valve 246 it will operate, however, the constriction valve 241 in series therewith provides a time delay in the fluid flow through the valve. The pressure buildup at relief valve 246occurs before the pressure in the system can be relieved through the constriction 214 described above. As can be seen from the foregoing, the series combination of constriction valve 241 and pressure relief valve 246 provides a time delay characteristic intermediate the long and instantaneous" time delays described.

While the embodiment shown in the drawings utilizes the three alternative flow paths to produce instantaneous,

short and long time delay characteristics for the circuit the drawings provides a range of tripping characteristics heretofore found only in drawout circuit breakers of much larger size and complexity.

The foregoing description has been based on the overload operation of one pole of a multi-pole unit. In the event that moderate overloads occur in more than one of the poles of a multi-pole circuit breaker, then only the most severely overload pole will control, i.e., no summing" of the individual inputs occurs. Referring to the drawings, it will be seen that the input elements are all connected in parallel by passageway 204; therefore, the hydraulic pressure at any one will be the same as at the others. If, for example, one pole has a greater overload then its input element would generate a given hydraulic pressure within the trip unit. This hydraulic pressure within the input element of the adjacent poles. Before the adjacent pole could make contribution to the internal hydraulic pressure, it must generate a force greater than the hydraulic pressure at its piston. The piston and piston rod assembly of each pole may be moved only when the internal pressure of the unit is overcome. It is on this basis that only the most severely overloaded pole will control operation of the trip unit.

Upon the operation of latch 158, which is at the single trip output point, the otherwise independent cradles 94 of the two actuating mechanisms 66 will both be released and will thus open all of the poles of the breaker. With removal of current flow through the current sensing units the input force to the trip unit falls to zero. The armatures 142 and input pistons 168 are returned to their rest position with the armatures against the adjusting screw 145 by the springs 146. Spring 194 drives piston 182 of the output element 156 to its zero input position and thereby causes the fluid between the diaphragm portion 186 and the bottom wall 192a of the bore to flow through the interconnecting passageways back to the input elements 154 from which it came. The formed portions 180 of the resilient diaphragm aid the return of the fluid to their respective bores.

The trip unit 126 including all the parts in FIGS. IX and X and all the parts acted upon by frames 2%, is removable as a unit when its connections to terminals 14 and conductors 118 are removed, by sliding the trip unit to the right and thus moving pins 284 along, and free of slots 286 in frames 290.

Referring to FIGS. XI and XII there is shown another embodiment in the invention wherein like parts are identified with the same reference numerals primed. In this embodiment of the invention the trip mechanism 126' is provided with a trip bar 300 that is pivotally mounted by end plates 302 on pins 304. The latch mechanism 158' is mounted on the trip mechanism 126' by a bracket 306. Spring 308 reacts between the trip bar and the brackets 302 to bias the trip bar in the relatching direction against frame carried stops 310. Each of the poles of this embodiment is provided with an input element 154 which engages the extension 148 of armature 142' intermediate its ends. The free end of the armature extension 148' engages the trip bar to effect release of the latch 158 when the armature 142 has moved a suificient distance toward the core against the resistance of the input element 154'. Adjustment of trip bar-to-latch travel distance is provided by screw 312. An element 156 corresponding to the output element 156 is provided; however, the piston rod 184 does not engage the trip bar; the element 156 acts as a single point loading or calibrating element for the trip point of the hydraulic system to which it is connected. The elements 154, 156 are connected by a hydraulic system identical to that shown in FIG. VIII. Pressure release means 234' and flow control means 214 function as in the previous embodiment. The mode of operation of this embodiment is as follows. Movement of the armature 142' toward the core 140' is resisted by armature return spring 146' and the input element 154'. The mechanical output of the armature is translated into hydraulic pressure within the trip unit 126 by input element 154 and is reflected by an increase in fluid pressure in the system and flow of fluid to the element 156'. The fluid is transmitted through the interconnecting passageways from the input elements 154 to the element 156 only when the pressure at element 156' overcomes the bias of its spring. The armature 142 is allowed to pivot as the piston rod Withdraws so that, when sufiicient force has been developed the armature extension 148' will drive the tripbar counterclockwise about its pivot 304 and thus release the latch 158' to effectuate operation of the release means. It should be noted that this embodiment is fail-safe in that if a leak should occur anywhere in the hydraulic system, then the resistance to the movement of the armature in the trip bar operating direction is reduced and trip unit will thus function at lower current levels. The operation of the flow control means 214' and the pressure release means 234' is the same in this embodiment as before, i.e., the flow control means 214 determines the time delay characteristic for moderate and long overloads while the pressure release means 234 determines the tripping mode for high overloads. Again only the most severely overloaded pole in a multi-pole breaker will control. Reset of the trip unit 126' occurs in the same manner as the reset of trip unit 126 previously described.

Referring to FIG. XIII there is shown yet another embodiment of the invention which is a modification of the embodiment shown in FIGS. XI and XII. Herein the trip bar mechanism 126" is provided with a trip bar 300' that is pivotally mounted on end plates 302 by pins 304. The latch mechanism 158" is mounted on the trip unit 126" as in FIG. XI. Spring 303 reacts between the trip bar 300' and the brackets 302 to bias the trip bar in the relatching direction against frame carried stops 310. Each of the poles of this embodiment is provided with an input element 154" which engages the extension 148" of armature 142 intermediate its ends. An element 156 corresponding to the output element 156 is provided and is adapted to engage the trip bar 300' on one side of its pivotal axis, that is, the axis determined by pins 304'. This embodiment is functionally similar to that shown in the FIGS. XI and XII previously described, however, output element 156 is operatively connected to the trip bar 300. Output element 156" is connected by passageways in the body of the trip mechanism 126" to the input elements 154". The input elements 154" are connected in parallel and are in turn connected to the output element 156" through flow control means and pressure release means, not shown, which are of similar construction to those previously disclosed. The mode of operation of this embodiment is as follows. Movement of armature 142" toward the core 140 is resisted by armature return spring 146 and the input element 154". The mechanical output of the armature 142" is translated into hydraulic pressure within the trip unit 126" by input element 154" and is reflected by an increase in fluid pressure in the system and flow of fluid to the output element 156". As the fluid is displaced from the input element to the output element 156" the output piston rod 184" is driven toward the trip bar 300'. When suflicient force has been generated by the input elements 154 the trip bar is caused to pivot and thereby operate the latch 158" through screw 312 to effectuate operation of the release means 66. The time delay and instantaneous operation are obtained by means of the flow control means and pressure release means, not shown, previously described. In the event that the system should leak the trip device 126" also operates in a fail-safe manner. The movement of the armature 142" toward its core 140", and thereby the movement 148' of the armature extension, is not resisted by the input element 154" and movement continues until the end of the armature extension 143" engages the trip bar 300 and causes the trip bar to pivot about its pins 304 in the cradle releasing direction without the benefit of any movement of the output element 155". Reset of trip unit 126 occurs in the same manner as the reset of trip units 126 and 126, previously described.

From the foregoing it will be appreciated that the illustrative embodiments of the invention have numerous features that result in improved operating characteristics.

Various modifications of the invention will readily occur to those skilled in the art and therefore the invention should be broadly construed in accordance with its full spirit and scope.

What is claimed is:

1. A multi-pole circuit breaker having a pair of separable contacts per pole, releasable means for separating said pairs of contacts, and overcurrent responsive means to eflect release of said releasable means upon the occurrence of a predetermined overcurrent condition in any one of said poles, said overcurrent responsive means including a current sensing element in each of said poles, said sensing element having mechanical output that varies in accordance with the current fiow in said pole, a single output element operatively connected to said releasable means, and hydraulic means interconnecting said plural current sensing elements and said single output element so that the output of any one of said sensing elements as caused by overcurrent conditions in its respective pole will actuate said output element to release said releasable means.

2. A mult-i-pole circuit breaker having a pair of separable contacts per pole, releasable means for separating said pairs of contacts, and overcurrent responsive means to eflect release of said releasable means upon the occurrence of a predetermined overcurrent condition in any one of said poles, said overcurrent responsive means including a current sensing element in each of said poles, said sensing element having mechanical output that varies in accordance with the current flow in said pole, at single output element operatively connected to. said releasable means, hydraulic means interconnecting said plural current sensing elements and said single output element so that the output of any one of said sensing elements as caused by overcurrent conditions will actuate said output element to release said releasable means, and time delay means interposed in said hydraulic system between said current sensing elements and said output element.

3. A multi-pole circuit breaker having a pair of separable contacts per pole, releasable means 'for separating said pairs of contacts, and overcurrent responsive means to effect release of said releasable means upon the occurrence of a predetermined overcurrent condition in any one of said poles, said overcurrent responsive means including a current sensing element in each of said poles, said sensing element having mechanical output that varies in accordance with the current flow in said pole, a single output element operatively connected to said releasable means, hydraulic means interconnecting said plural current sensing elements and said single output element so that the output of any one of said sensing elements as caused by overcurrent conditions will actuate said output element to release said releasable means, and plural time delay means interposed in said hydraulic system between said current sensing elements and said output element, said time delay means being connected in parallel to provide alternate communicating paths between said current sensing elements and said output element.

4. A multi-pole circuit breaker having a pair of separable contacts per pole, releasable means for separating said pairs of contacts, latch means for said releasable means, and overcurrent responsive means for operating said latch means to eflect release of said releasable means upon the occurrence of a predetermined overcurrent condition in any one of said poles, said overcurrent responsive means including a current sensing element in each of said poles, said sensing element having a mechanical output that varies in accordance with the current flow in said pole, a trip bar extending across all of said poles and operatively connected to said latch means, an output element for driving said trip bar to operate said latch means, fiuid means interconnecting said plural current sensing elements and said single output element so that the output of any one of said sensing elements as caused by overcurrent conditions will actuate said output element to drive said trip bar to release said latch means, and mechanical means in addition to said fluid means interconnecting said current sensing element and said trip ba-r whereby said trip bar may be driven directly to release said latch in the event of failure of said fluid system.

S. A multi-pole circuit breaker having a pair of separable contacts per pole, releasable means for separating said pairs of contacts, latch means for said releasable means, and overcurrent responsive means for operating said latch means to eifect release of said releasable means upon the occurrence of a predetermined overcurrent condition in any one of said poles, said overcurrent responsive means including a current sensing element in each of said poles, said sensing element having a mechanical output that varies in accordance with the current flow in said pole, a trip bar extending across all of said poles and operatively connected to said latch means, mechanical means interconnecting said current sensing elements and said trip bar so that movement of said sensing element upon the occurrence of overcurrent conditions is translatable into tr-ip bar operation, a single calibrating element, and fluid means interconnecting all of said plural current sensing elements and said calibrating element so that single point adjustment of the mechanical force to be overcome by said sensing elements in order to operate the trip bar may be had.

6. A multi-pole circuit breaker having a pair of separablecon-tacts per pole, releasable means for separating said pairs of contacts, latch means for said releasable means, and overcurrent responsive means for operating said latch means to effect release of said releasable means upon the occurrence of a predetermined overcurrent condition in any one of said poles, said overcurrent responsive means including a current sensing element in each of said poles, said sensing element having a mechanical output that varies in accordance with the current flow in said pole, an output element operatively connected to saidlatch means, and fluid means interconnecting said plural current sensing elements and said single output element so that the output of any one of said sensing elements as caused by overcurrent conditions will actuate said output element to release said latch means.

7. A multi-pole circuit breaker having a pair of separable contacts per pole, releasable means for separating said pairs of contacts, latch means for said releasable means, and overcurrent responsive means for operating said latch means to effect release of said releasable means upon the occurrence of a predetermined overcurrent condition in any one of said poles, said overcurrent responsive means including a current sensing element in each of said poles, said sensing element having a mechanical output that varies in accordance with the current flow in said pole, an output element operatively connected to said latch means, fluid means interconnecting said plural current sensing elements and said single output element so thatthe output of any one of said sensing elements as caused by overcurrent conditions will actuate said output element to release said latch means, and time delay means interposed in said fluid system between said current sensing elements and said output element.

8. A multi-pole circuit breaker having a pair of separable contacts per pole, releasable means for separating said pairs of contacts, latch means for said releasable means, and overcurrent responsive means for operating said latch means to effect release of said releasable means upon the occurrence of a predetermined overcurrent condition in any one of said poles, said overcurrent responsive means including a current sensing element in each of said poles, each said sensing element having a mechanical output in the form of fluid displacement that varies in accordance with the current flow in said pole, a single output element operatively connected to said latch means, and fluid means interconnecting said plural current sensing elements and said single output element so that the output of any one of said sensing elements as caused by overcurrentconditions will displace said output element to release said latch means, said fluid means including means defining a first fluid coupling interconnecting said sensing elements, means defining second and third fluid couplings both interconnecting said first fluid coupling and said output element, fluid flow restriction means in said second fluid coupling to limit the rate of flow of fluid therethrough, pressure responsive means in said third fluid coupling, said pressure responsive means blocking fluid flow through said third fluid coupling at pressure below a given magnitude and allowing flow therethrough at pressure above said given magnitude, said flow restriction means providing time-delay operation of said output ele ment, said pressure responsive means providing instantaneous operation of said output element so that the output of any one of said sensing elements as caused by overcurrent conditions in its pole will actuate said output element, biasing means rendering said output element inoperative at fluid pressure below a given value, and means for adjusting said biasing means.

9. A multi-pole circuit breaker having a pair of separable contacts per pole, releasable means for separating said pairs of contacts, latch means for said releasable means, and overcurrent responsive means for operating said latch means to effect release of said releasable means upon the occurrence of a predetermined overcurrent condition in any one of said poles, said overcurrent responsive means including a current sensing element in each of said poles, each said sensing element having a mechanical output in the form of fluid displacement that varies in accordance with the current flow in said pole, a single output element operatively connected to said latch means, and fluid means interconnecting said plural current sensing elements and said single output element so that the output of any one of said sensing elements as caused by overcurrent conditions will displace said output element to release said latch means, said fluid means including means defining a first fluid coupling interconnecting said sensing elements in parallel, means defining second, third and fourth fluid couplings providing parallel fluid flow paths interconnecting said first fluid coupling and said output element, fluid flow restriction means in said second fluid coupling to limit the rate of flow of fluid therethrough, pressure responsive means in said third fluid coupling, serially connected fluid flow restriction means and pressure responsive means in said fourth fluid coupling, said pressure responsive means blocking fluid flow through said fluid couplings at pressures below a given magnitude and allowing flow therethrough at pressure above said given magnitude, said flow restriction means providing timedelay operation of said output element, said pressure responsive means providing faster operation of said output element so that the output of any one of said sensing elements as caused by overcurrent conditions in its pole will actuate said output element, biasing means rendering said output element inoperative at fluid pressure below a given value, and means for adjusting said biasing means.

10. A multi-pole circuit breaker having a pair of separable contacts per pole, releasable means for separating said pairs of contacts, latch means for said'releasable means, and overcurrent responsive means for operating said latch means to eflect release of said releasable means upon the occurrence of a predetermined overcurrent condition in any one of said poles, said overcurrent responsive means including a current sensing element in each of said poles, said sensing element having an output that varies in accordance with the current flow in said pole, a single output element operatively connected to said latch means, and fluid means interconnecting said plural current sensing elements and said single output element, said fluid means including a mounting block, said block having input means for each pole operatively connected to the current sensing element in said pole, said input means being adapted to vary the fluid pressure in said fluid means in response to the operation of the respective ones of said current sensing elements, means defining a first passageway in said mounting block for interconnecting said input means, means defining second and third passageways respectively in said mounting block, said second and third passageways interconnect-ing said first passageway and said output element, an adjustable flow control valve in said second passageway to control the rate of flow of fluid therethrough, a preloaded pressure relief valve in said third passageway, said relief valve being normally closed and blocking fluid flow through said third passageway at pressures below a given magnitude and being open to allow fluid flow therethrough at pressures above said given magnitude, said output element being fluid pressure operated, said flow control valve providing time-delay operation of said output element so that the output of any one of said sensing elements as caused by overcurrent conditions Will actuate said output element to release said latch means.

11. A multi-pole circuit breaker having a pair of separable contacts per pole, releasable means for separating said pairs of contacts, latch means for said releasable means, and overcurrent responsive means for operating said latch means to effect release of said releasable means upon the occurrence of a predetermined overcurrent condition in any one of said poles, said overcurrent responsive means including a cur-rent sensing element in each of said poles, said sensing element having an output that varies in accordance with the current flow in said pole, a single output element operatively connected to said latch means, and fluid means interconnecting said plural current sensing elements and said single output element, said fluid means including a mounting block, said block having input means for each pole operatively connected to the current sensing element in said pole, said input means being adapted to vary the fluid pressure in said fluid means in response to the operation of the respective ones of said current sensing elements, means defining a first passageway in said mounting block for interconnecting said input means, means defining second, third and fourth passageways respectively in said mounting block, said second, third and fourth passageways interconnecting said first passageway and said output element, an adjustable flow control valve in said second passageway to control the rate of flow of fluid therethrough, a pre-loaded pressure relief valve in said third passageway, a serially connected flow control valve and pro-loaded pressure relief valve in said fourth passageway, said relief valves being normally closed and blocking fluid flow through said passageways at pressures below a given magnitude and being open to allow fluid flow therethrough at pressures above said given magnitude, said output element being fluid pressure operated, said flow control valves providing time-delay operation of said output element so that the output of any one of said sensing elements as caused by overcurrent conditions will actuate said output element to release said latch means.

12. A circuit breaker according to claim 1 wherein the output element includes biasing means rendering said element inoperative at fluid pressures below a given value, and means for adjusting said biasing means.

13. Overcurrent release means for automatically controlling a multi-pole circuit breaker for opening the contacts thereof comprising a trip unit mounting block, a magnetic core and armature structure for each pole carried by said block, said core adapted to surround a current carrying member, a current sensing element having mechanical output mounted adjacent each of said armatures, said armature being attracted to said core in response to current flow through said current carrying member, each said sensing element being operatively connected to the adjacent armature so that the mechanical output of the sensing element varies in accordance with the current flow in said pole, each of said sensing elements including a piston movable in a bore formed in said block to provide fluid displacement, a system of fluid filled passageways in said block, a single output element for said trip unit movable in response to fluid displacement, said output element comprising a piston movable in a bore in said block, means defining a first passageway in said block for interconnecting the bores of said input means, means defining second and third passageways respectively in said block, said second and third passageways both interconnecting said first passageway and the bore of said output element, an adjustable flow control valve in said second passageway to control the rate of flow of fluid therethrough, a pressure relief valve in said third passageway, said relief valve being normally closed and blocking flow fluid through said third passageway at pressures below a given magnitude and being open to allow fluid flow therethrough at pressures above said given magnitude, said output element being displaceable in response to change in fluid pressure within the bore thereof, said flow control valve providing time-delay operation of said output element, said relief valve providing instantaneous operation of said output element so that the output of any one of said sensing elements as caused by overcurrent conditions in its pole will actuate said output element, biasing means rendering said output element inoperative at fluid pressure below a given value, and means for adjusting said biasing means.

14. Overcurrent release means for automatically controlling a multi-pole circuit breaker for opening the contacts thereof comprising a magnetic core and armature structure for each pole, ,an overcurrent sensing element x 16 mounted adjacent each of said armatures, each said sensing element mounted adjacent each of said armatures, each said sensing element being operatively connected to the adjacent armature and having a mechanical output in the form of fluid displacement which varies in accordance with the current flow in said pole, an output element movable in response to fluid displacement, means defining a first passageway for interconnecting said input means, means defining second and third passageways respectively, said second and third passageways both interconnecting said first passageway and said output element, an adjustable flow control valve in said second passageway to control the rate of flow of fluid therethrough, a pressure relief valve in said third passageway, said relief valve being normally closed and blocking flow fluid through said third passageway at pressures below a given magnitude and being open to allow fluid flow therethrough at pressures above said given magnitude, said flow control valve providing time-delay displacement of said output element, said relief valve providing instantaneous displacement of said output element so that the output of any one of said sensing elements as caused by overcurrent conditions in its pole will actuate said output element, biasing means rendering said output element immovable at fluid pressure below a given value, and means for adjusting said biasing means.

15. Overcurrent release means for automatically controlling a circuit breaker for opening the contacts thereof comprising a trip unit mounting block, plural magnetic core and armature structures mounted on said block, an overcurrent sensing element mounted adjacent each of said armatures, each said sensing element being operatively connected to the adjacent armature and leaving mechanical output in the form of fluid displacement which varies in accordance with the current flow in said pole, each of said sensing elements comprising a piston movable in a bore formed in said block, a single output element for said trip unit, said output element comprising a piston movable in a bore in said block, means defining a first fluid coupling interconnecting said input means, means defining second and third fluid couplings both interconnecting said first fluid coupling and said output element, fluid flow restriction means in said second fluid coupling to limit the rate of flow of fluid therethrough, pressure responsive means in said third fluid coupling, said pressure responsive means normally blocking flow fluid through said third fluid coupling at pressure below a given magnitude and being open to allow fluid flow therethrough at pressures above said given magnitude, said flow restriction means providing time-delay operation of said output element, said pressure responsive means providing instantaneous operation of said output element so that the output of any one of said sensing elements as caused by overcurrent conditions in its pole will actuate said output element, biasing means rendering said output element inoperative at fluid pressure below a given value, and means for adjusting said biasing means.

16. Overcurrent release means for automatically controlling a multi-pole circuit breaker for opening the contacts thereof comprising a trip unit mounting block, a trip bar pivoted on said block, a magnetic core and armature structure for each pole carried by said block, an overcurrent sensing element mounted adjacent each of said armatures, said sensing element being operatively connected to the adjacent armature so that the mechanical output of the sensing element in the form of fluid displacement varies in accordance with the current flow in said pole, each of said sensing elements including a piston movable in a bore formed in said block, a single output element for said trip unit movable in response to fluid displacement and adapted to engage said trip bar to effect opening of the contacts, said output element comprising a piston movable in a bore in said block, means defining a first passageway in said block for interconnecting the bores of said input means, means defining second and third passageways respectively in said block, said second and third passageways both interconnecting said first passageway and the bore of said output element, an adjustable flow control valve in said second passageway to control the rate of flow of fluid therethrough, a pressure relief valve in said third passageway, said relief valve being normally closed and blocking flow fluid through said third passageway at pressures below a given magnitude and being open to allow fluid flow therethrough at pressures above said given magnitude, said output element being displaceable in response to change in fluid pressure within the bore thereof, said flow control valve providing time-delay oper ation of said output element, said relief valve providing instantaneous operation of said output element so that the output of any one of said sensing elements as caused by overcurrent conditions in its pole will actuate said output element, biasing means rendering said output element inoperative at fluid pressure below a given value, means for adjusting said biasing means, said trip bar and said armature being provided with mutually engaging portions to effect operation of said trip bar when said output element is rendered nonresponsive due to fluid response failure.

No references cited.

BERNARD A. GILHEANY, Primary Examiner. 

1. A MULTI-POLE CIRCUIT BREAKER HAVING A PAIR OF SEPARABLE CONTACTS PER POLE, RELEASABLE MEANS FOR SEPARATING SAID PAIRS OF CONTACTS, AND OVERCURRENT RESPONSIVE MEANS TO EFFECT RELEASE OF SAID RELEASABLE MEANS UPON THE OCCURRENCE OF A PREDETERMINED OVERCURRENT CONDITION IN ANY ONE OF SAID POLES, SAID OVERCURRENT RESPONSIVE MEANS INCLUDING A CURRENT SENSING ELEMENT IN EACH OF SAID POLES, SAID SENSING ELEMENT HAVING MECHANICAL OUTPUT THAT VARIES IN ACCORDANCE WITH THE CURRENT FLOW IN SAID POLE, A SINGLE OUTPUT ELEMENT OPERATIVELY CONNECTED TO SAID RELEASABLE MEANS, AND HYDRAULIV MEANS INTERCONNECTING SAID PLURAL CURRENT SENSING ELEMENTS AND SAID SINGLE OUTPUT ELEMENT SO THAT THE OUTPUT OF ANY ONE OF SAID SENSING ELEMENTS AS CAUSED BY OVERCURRENT CONDITIONS IN ITS RESPECTIVE POLE WILL ACTUATE SAID OUTPUT ELEMENT TO RELEASE SAID RELEASABLE MEANS. 